1. Field of the Invention
This invention relates to improvements in a seatbelt tightening device wherein a seatbelt is tightened to remove a sag therefrom in a collision of a motor vehicle.
2. Description of the Prior Art
In general, a seatbelt for restraining an occupant in a collision or the like of a motor vehicle is adapted to lock the seatbelt by an emergency lock device in a collision, to thereby prevent the seatbelt from being unwound. However, if there is a sag in the seatbelt in a locked state of the seatbelt, then the effect of restraining the occupant by the seatbelt is diminished.
As a means for removing a sag from the seatbelt; a seatbelt tightening device for tightening the seatbelt in a collision of a motor vehicle is proposed. There is proposed such a seatbelt tightening system, which uses a restoring force of a spring for example, that the spring in a compressed state is adapted to be released by a trigger mechanism for sensing a change in acceleration such as a pendulum. However, there have been presented the disadvantage that it takes a long time from an occurrence of a collision to completion of operation of the trigger mechanism, whereby the timing of tightening the seatbelt tends to be delayed. Further, there has been proposed one in which the device is engaged with a moving body such as a body of rotation under a frictional force, to thereby tighten the seatbelt. However, there has been presented the disadvantage of low reliability.